Trapezoid ABCD has AB || CD, BC = CD = 43, and AD ⊥ BD. Let O be the intersection of the diagonals AC and BD, and let P be the midpoint of BD. Given that OP = 11, the length AD can be written in the form m√n, where m and n are positive integers and n is not divisible by the square of any prime. What is m + n?